1. Field of the Invention
This invention relates to chemical mixing, and more particularly to the treatment of a liquid with a chemical.
2. Background of the Invention
The treatment and disposal of wastewater is an ever increasing problem as the population and subsequent urbanization increases. Ultimate disposal of wastewater is either to discharge into a surface body of water or in some areas subsurface disposal is utilized. In both instances, treatment of wastewater prior to disposal is mandatory to prevent both the water quality and the health and safety of the public to be compromised. Wastewater contains, among other contaminants, suspended particulate matter, biodegradable organic material and pathogenic bacteria. The pathogenic bacteria must be destroyed and particulates and biodegradables must be removed in order to achieve the effluent water quality standards required for environmental release. Additionally, removal of toxic and industrial wastes as well as nitrates and phosphates must be accomplished prior to release.
There are three levels of wastewater treatment, namely a primary level of treatment, a secondary level of treatment and a tertiary level of treatment. The primary level of treatment is usually a first step in the treatment of wastewater. The primary level of treatment removes approximately 60 percent of the total suspended solids and about 35 percent of the BOD (Biochemical Oxygen Demand) materials. After the primary level of treatment, dissolved impurities remain in the wastewater.
The secondary level of treatment removes approximately 85 percent of both the solid suspended matter and BOD. The secondary level of treatment is the generally required minimum in developed countries such as the United States.
The tertiary level of treatment is used to provide cleaner water. Although the tertiary level of treatment is expensive, very often doubling the cost of the secondary treatment, the effluent water discharged from the tertiary level of treatment is of near drinking water quality.
A final step in the wastewater treatment process is an effluent disinfection process. The effluent disinfection process normally requires the effluent to be mixed with chlorine gas in a contact tank. Unfortunately, chlorine gas leaves a chlorine residue that may have adverse effects on aquatic life. Other forms of effluent disinfection such as ultraviolet radiation are becoming competitive with the use of chlorine gas.
One example of these new techniques is Primary treatment removal of material which floats on the surface of the wastewater, or material that settles out due to the force of gravity. These treatments include the processes of comminuters, or grinding the waste, screening, grit removal and sedimentation.
Secondary wastewater treatment comprises the removal of colloidal particles. A colloidal dispersion is a suspension of finely divided particles in a continuous medium. The particles typically range in size between 10−4 to 10−7 centimeters. Since the particles have a net electrical charge, the particles tend to repel each other, and tend to stay in suspension, rather than coagulate and precipitate. The charge on the suspended particles can be neutralized through the addition of an electrolyte to the suspension. Following the neutralization of the suspended particles, the particles begin to coagulate and form larger particles.
Several secondary treatment processes have been developed to remove contaminants from the wastewater. In one process, an electrolyte is added and mixed with the wastewater to neutralize the suspended particle charge. After the charge on the suspended particle is neutralized, an anionic polymer is added and mixed with the wastewater. The anionic polymer results in the further particle association and the formation of loose aggregations or soft flakes of particles called flocculates or flocs. The flocs with a density greater than water settle and form sludge, while the less dense material rises to the surface and forms a scum. Both the sludge and scum are readily removed from the water for disposal, while the water is further processed as needed.
The prior art addresses many of the concerns in the treatment of wastewater, however several problems associated with these processes have not been answered. Among these problems is the build-up of material on and around the internal mechanisms associated with the process. The following U.S. Patents represent some of the attempts of the prior art to resolve the above problems.
U.S. Pat. No. 4,111,402 to Richard J. Barbini teaches a motionless mixer for combining different substances brought into communication therewith. The mixer includes at least two tubular members. Each tubular member has at least one spiral corrugated surface thereon. The members are arranged so that different substances brought into and out of communication therewith including the at least one corrugated surface will be mixed together.
U.S. Pat. No. 4,462,903 to Dietmar Wettengl teaches a device for the catalytic oxidation purification of waste water inside a reaction vessel. The vessel includes a front wall, a back wall, two side walls interconnecting the front and back wall and a bottom. The waste water is admitted into the vessel through admitting means located on the front wall and discharged through discharge means located on the back wall. The vessel is divided into a plurality of compartments each of which includes a pair of risers which are divided by a plurality of partitions to form a plurality of sub-chambers. The partitions include an oscillatable flap or, alternatively, are tilted in a direction opposite to the direction of flow of the water in the vessel. In this manner, entrapment of the catalyst particles is prevented.
U.S. Pat. No. 4,576,714 to Anton P. Pohoreski teaches a novel sewage purification system. The system includes a pump for drawing sewage into the system and an injection inlet for injecting chemical into the effluent line from the pump. The pump leads to a pair of interconnected U-shaped mixing chambers connected to the effluent line from the pump, the U-shaped mixing chambers being baffled and being of a particular construction. There is also a recycle line from the inlet line to the mixing chambers back to the pump for recycling about 1–20% of the total flow rate, which is generally about 5–40 gallons/minute through the system. The U-shaped mixing chambers are also provided with at least two injection inlets for injecting chemicals thereinto. A splitter chamber is connected to the outlet from the mixing chambers to provide a pair of parallel flow outlets therefrom. A separator chamber is connected to the parallel flow outlets, the separator chamber having structure therein for providing tangential flow along the inside walls and also for separating sludge therefrom and for withdrawing it from the bottom thereof, and for withdrawing clean water from the upper central core thereof. Finally, a sludge removal line is provided, along with a sludge recycle line for recycling about 1–20% of the sludge back to the pump inlet line.
U.S. Pat. No. 4,710,290 to Raymond P. Briltz teaches chemicals added to a fluid such as sewage to flocculate and precipitate solids therefrom. The solids are deflected downwardly and sink by gravity to the base of an elongated chamber so that the substantially clarified fluid flows over a weir at one end of the chamber with the flocculated and precipitated material forming a sludge in the base thereof. Whereafter, the sludge may be removed either through a fluid lock device or pressurizing the system to stratify the flow and provide still areas for the sludge to settle through the fluid and be removed as required.
U.S. Pat. No. 5,013,429 to Milos Krofta teaches an apparatus and method for stabilizing sludge such as the sludge produced by municipal waste water treatment plants. It includes thickening of the sludge to a dry solid content in the range of 3% to 8% before feeding it to at least one comparatively small reactor tank that extends horizontally and has an inlet and outlet adjacent opposite end walls. The system preferably utilizes multiple tanks stacked one above the other and connected in series. The tanks have an in-built mixer that sweeps through the interior of the tank. The mixer is eccentrically mounted so that its mixing members carry the sludge through the uppermost portion of the tank interior and are spaced from the bottom surface of the tank. A sparger is located either in the inlet or in the bottom clearance of the tank to introduce microscopic bubbles of oxygen and ozone into the sludge. A pressure regulating valve controls the flow of the stabilize sludge from the uppermost reactor tank. The pressure regulating valve and the metering pump together maintain a hyperbaric pressure within the tanks.
U.S. Pat. No. 5,120,436 to Thomas W. Reichner teaches contaminated liquid or sludge clarification accomplished by the use of a basic one or a series of operatively connected and vertically extending units or devices of the invention. Each of which employs a hose that is spiraled around a cylindrical container wall whose upper end is open to an overflow weir from which recovery of lower specific gravity clarified liquid is effected and whose lower end is open and connected to a cone or funnel-shaped wall that defines a receiving and delivering chamber for separated-out heavier specific gravity contaminating liquid, sediment, viscous or thickened material. The hose of the basic unit is adapted at its upper end to receive the contaminated liquid, sludge or the like and any suitable chemical flocculant, precipitant, or coagulant, such as a polyelectrolyte, that may be injected or added to the contaminated liquid before it is introduced therein. The hose is adapted to thoroughly mix the heavier specific gravity material content with the coagulant as the liquid charge moves downwardly in a somewhat slowly swirling path therein. A nozzle is connected to the lower end and along the inside of a lower end portion of the cylindrical wall to deliver its contents in a substantially vertically laminated relation within the container above and adjacent to an upper end portion of the cone-shaped wall.
U.S. Pat. No. 5,145,256 to Wiemers et al. teaches an apparatus and method for treating effluents for selective solids control and/or dewatering of effluents, for example drilling fluids (or mud), slurries or sludges, or other clean up involving solids removal from a hydraulic system where flocculation would be employed. The apparatus is compact and portable for ease of on-site delivery and hookup and includes a plurality of mixers for mixing polymer materials with water and/or the effluent, a plurality of pumps for controlling the flow of effluents, water and mixed liquids, and a plurality of conveniently located valves and pump controls for control of the various functions of the apparatus from a centrally located control panel. An improved mixing device is provided for blending of shear-sensitive fluids which includes multi-port injection sites and a series of geometrical flow altering elements. A device for wetting dry particulate material in a liquid feed stream is provided having a cylindrical funnel eductor and a cyclonic dispersal eductor.
U.S. Pat. No. 5,145,256 to Wiemers et al. teaches an apparatus and method for treating effluents for selective solids control and/or dewatering of effluents, for example drilling fluids (or mud), slurries or sludges, or other clean up involving solids removal from a hydraulic system where flocculation would be employed. The apparatus is compact and portable for ease of on-site delivery and hookup and includes a plurality of mixers for mixing polymer materials with water and/or the effluent, a plurality of pumps for controlling the flow of effluents, water and mixed liquids, and a plurality of conveniently located valves and pump controls for control of the various functions of the apparatus from a centrally located control panel. An improved mixing device is provided for blending of shear-sensitive fluids which includes multi-port injection sites and a series of geometrical flow altering elements. A device for wetting dry particulate material in a liquid feed stream is provided having a cylindrical funnel eductor and a cyclonic liquid flowing through the chamber.
Therefore, it is an object of the present invention to provide an improved apparatus and method for the treatment of a liquid that overcomes the inadequacies of the prior art and provides a significant contribution to the art.
Another object of this invention is to provide an improved apparatus and method that is suitable for treating wastewater.
Another object of this invention is to provide an improved apparatus that provides a substantially reduced flow restriction to matter flowing therethrough.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed as being merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention with in the scope of the invention. Accordingly other objects in a full understanding of the invention may be had by referring to the summary of the invention, the detailed description describing the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.